Large-scale fabrication of hard superlattice thin films by combined steered arc evaporation and unbalanced magnetron sputtering

This paper reports on the mechanical and physical properties of a range of TiAlN- and TiN-based polycrystalline superlattice hard coatings fabricated by a combined steered are evaporation and unbalanced magnetron sputter industrial batch process within a common gas atmosphere. The reactive deposition experiments were carried out in a four-cathode system in which the substrates could be continuously rotated at a nominal target-substrate distance of 250 mm and with variable velocity. The influence of layer composition, deposition technique, substrate rotation and coating rate were investigated by XTEM, XRD, RES and Knoop indentation testing with regard to the superlattice period and microstructure, and the preferred orientation and hardness of the coatings. All coatings were found to exhibit fine, highly dense lamella microstructure, high hardness and excellent adhesion. Film systems deposited by closed-field unbalanced magnetron sputtering could exhibit preferred [111] growth, whilst coatings deposited by simultaneous steered arc/unbalanced magnetron sputtering generally showed [200] orientation. The period of the superlattice could be controlled between 19 and 172 Angstrom by alteration of the substrate rotation and deposition rate. (C) 1997 Elsevier Science S.A.